1. Field of the Invention
The present invention relates to an end of a side-looking endoscope, and in particular, to an end of a side-looking endoscope having a cap detachably affixed on an end body.
2. Description of the Related Art
A side-looking endoscope is intended to observe the inside of an observed body on a side of its end from an observation port on a side surface of its end and to lead various treatment devises such as forceps to the inside of the observed body on the side of its end via a treatment devise insertion channel provided inside so as to perform an incision, a biopsy, recovery of the contents and so on therewith.
An end of the endoscope has a metallic end body, and there is a problem that, if such an end body is in direct contact with mucous membranes of a patient, it may hurt them. For this reason, a cap made of rubber or the like for covering the end body is detachably affixed on the end body. The cap is formed by an elastic material, and has a circular minor diameter portion provided projectingly toward the inside on an inner radius surface close to its rear end. This minor diameter portion is fitted into a circumferential groove formed on a peripheral surface of the end body so as to lock the cap on the end body. There is a possibility that the cap may drop off the end body or rotate if forcefully passed through a narrowed area in the body during endoscopy. Japanese Patent Application Publication No. 9-253036 discloses that a detent member is affixed on the end body so that the rotation and drop of the cap is thereby prevented. This construction has, however, a problem that the detent member is a separate part from the end body, and also a problem that, if the detent member is formed as one with the end body, it is shaped astride a treatment devise insertion slot so that its structure and manufacturing become complicated.
An endoscope has an airtight optical system accommodation room provided inside the end body. An image-taking optical system such as a CCD and an illumination optical system such as a light guide are accommodated in this accommodation room. If the image-taking optical system and the illumination optical system are accommodated in separate rooms, each room becomes smaller so that workability deteriorates. Japanese Patent Application Publication No. 8-76028 discloses an endoscope accommodating the image-taking optical system and the illumination optical system in a common large optical system accommodation room. According to this endoscope, the accommodation room has such a wide frontage that it is easy to incorporate the image-taking optical system and the illumination optical system therein.
This construction, however, has a problem that its frontage is widened and so the airtight surface becomes too wide to be kept airtight. In particular, in the case where a metal sheet to be a lid of the accommodation room is adhered to the end body with an adhesive, there arises a problem that airtightness is reduced in conjunction with degradation of the adhesive. Furthermore, there is a problem that the metal sheet is exfoliated from the airtight surface of the end body by a springback to reduce the airtightness.
To prevent this, it is thinkable to fix the metal sheet with screws at a plurality of locations and thereby secure the airtightness. However, there is a problem that it is not possible to take enough space for screwing it at a plurality of locations due to high density of component members at the end of the endoscope, that is, the optical system accommodation room in particular.